Perioperative ketamine does not prevent chronic pain after thoracotomy

Thoracotomy is often responsible for chronic pain, possibly of neuropathic origin. To confirm preclinical studies, the preventive effects of perioperative ketamine were tested in a randomized, double-blind, placebo-controlled clinical trial on persistent neuropathic pain after thoracotomy. Eighty-six patients scheduled for thoracotomy under standardised general anaesthesia were randomised to receive either ketamine (1 mg kg(-1) at the induction, 1 mg kg(-1) h(-1) during surgery, then 1 mg kg(-1) during 24 h; n=42) or normal saline (n=44). Postoperative analgesia included a single dose of intrapleural ropivacaine, intravenous paracetamol and nefopam, and patient-controlled intravenous morphine. Vital parameters and analgesia were recorded during the 48 first postoperative hours. Seventy-three patients were followed up. The patient's chest was examined 1-2 weeks, 6 weeks and 4 months after surgery. At the last two observations, spontaneous pain score over a one-week period (visual analogue scale), neuropathic pain score (NPSI), and intake of analgesics, were assessed. No drug affecting neuropathic pain (except opiates) was given during the follow-up. Two patients in each group were lost to follow-up after the 6 week visit. Ketamine improved immediate postoperative pain, but the groups were similar in terms of neuropathic pain and intake of analgesics, 6 weeks (NPSI score: ketamine: 1.25 [0-4.125]; placebo: 1 [0-4]) and 4 months after surgery. Thus, ketamine given in 24-h infusion failed to prevent chronic neuropathic pain after thoracotomy. Other perioperative preventive long-lasting treatments or techniques could be tested in this context.